Washington: Researchers have linked a second type of mouse virus to a baffling condition called chronic fatigue syndrome, but said their findings do not yet prove that any virus causes the symptoms.
They found evidence of murine leukemia virus, which causes cancer in mice, in 86 percent of chronic fatigue patients they tested, but in fewer than 7 percent of healthy blood donors.
The team, lead by Harvey Alter of the National Institutes of Health, said much more study is needed to determine how common the virus is in people and whether it might be causing disease, or whether it is an innocent bystander.
But they say their finding adds to evidence that viruses may be linked with the debilitating condition.
It is the second mouse virus to be linked to chronic fatigue syndrome. Another study in 2009 found xenotropic murine leukemia virus-related virus or XMRV in some patients with chronic fatigue syndrome but several others since then have found no such link.
Evidence of XMRV has also been found in prostate tumours, but again, scientists are unsure if the virus may actually be causing the tumours.
Writing in the Proceedings of the National Academy of Sciences, the researchers stressed that the study raises at least as many questions as it answers and said it is too soon to say that viruses cause chronic fatigue syndrome.
"Chronic fatigue syndrome is a debilitating disorder defined solely by clinical symptoms," the researchers wrote. There is no good test for the syndrome, which can leave patients unable to work.
Bureau Report
